Remote control system for radio receivers and the like



Aug. 29, 1944. M. THOMPSQN 2,357,237

REMOTE CONTROL SYSTEM FOR RADIO RECEIVERS AND THE LIKE 3 Sheets-Shet 1 Filed July 20, 1938 LOWE/ SUPPL Y ,2

UNIT

REMOTE CONTROL SYSTEM FOR RADIO RECEIVERS AND THE LIKE M. THOMPSON 2,35 7237 Filed July 20, 1938 5 Sheets-Sheet 2 AMA AMA M AMA AMA vvv vvv vvv vw vvv 5 C, 0 -5. n m H mm ml mmmmmmmmnmmmnH H HHHIIIHHHIHHHHHHHHHHHI hmmnmmnnml uuuumuuumu nu m m H! M. THOMPSON REMOTE CONTROL SYSTEM FOR RADIO RECEIVERS AND THE LIKE Filed July 20, 1938 3 Sheets-Sheet 5 AAAAA vvvvvv I 60 J6 J9 e4 4/ I 50 Patented Aug. 29, 1944 REMOTE CONTROL SYSTEM FOR RADIO RECEIVERS AND THE LIKE Milton L. Thompson, Philadelphia, Pa., assignor, by mesne assignments, to Philco Radio and Television Corporation, Philadelphia, Pa., a corporation of Delaware Application July 20, 1938, Serial No. 220,356

36 Claims.

This invention relates to a remote control system for controlling radio receivers and the like from a distance, and more particularly to a remote control system wherein the control action is effected without the use of a physical connection or connections between the radio receiver and the point of control.

It is highly desirable to be. able to control both the tuning and the volume level of a radio receiver from a distance, as from across a room or from an adjacent room. Remote control of the volume is important because it permits of an accurate adjustment in accordance with the strength of the desired signal being received and the distance of. the listener from the receiver.

By the present invention, all interconnecting cables are eliminated by employing inductive coupling between the radio receiver and the remotely located control means. Briefly, this may be accomplished according to the invention by providing the receiver with electrical, mechanical, or electro-mechanical tuning and volume control means responsive to suitable control signals, whereby the receiver circuits may be automatically adjusted. to receive any desired intel-v ligence signal at any desired volume level. The control signals may be provided at the pointof remote control by means of a low power miniature generator capable of supplying proper signals at the receiver. The generator may be so arranged as to produce a series of pulses of a character determined by an operator at the remote location. One of the possible methods of producing the control signals at the remote point is by the use of an impulse sender which keys the generator and thus determines the form, spacing, length, and number of the control signals in response to simple operations on the part of the operator. These generated pulses may be conveyed by means of inductive coupling to suitable means located at the radio receiver, there converted into a corresponding series of direct current pulses, and utilized to operate apparatus comprising electrical, mechanical, or electro-mechanical means, thereby actuating the tuning and/or volume control means of the receiver in accordance with the received control signals. The inductive coupling existing between the generator means and the means located at the radio receiver may be obtained by providing coils at these points whose construction and relative orientation are such that, notwithstanding separations, for example, of 75 feet or more, an adequate value of mutual inductance is obtained therebetween to ensure that the generated medium frequency signal current existing in the remotely located coil will. inductively produce similar signal currents in the coupled coil of suflicient magnitude to permit their detection by suitable means.

In the case of volume control or the like it is provided, in accordance with the invention that a preliminary signal or signalsfirst produceeffects which so arrange the receivers control means that the subsequent control signal will produce the desired volume level changes, the degree of variation or change being dependent on the length of the control signal.

One of the problems which required solution had to do with the difliculty occasioned by the arrival of noise pulses which often resulted in undesired and. highly erratic actuation of the receivers remotely controlled tuning and/or volume control means. As will be explained in more detail hereinafter various means have been devised to protect the control circuits from these noise pulses. One of these means provides that the first control pulse or pulses received advance the control apparatus only to inoperative or dead positions. Then preferably one or more of the subsequent pulses may be employed to effect the control of those receiver functions which are not particularly sensitive to small control variations such as might be occasioned by the arrival of short, widely-spaced noise pulses. Volume or tone control are illustrative of this class of function. On the other hand, the more sensitive receiver functions, such as tuning, are preferably capable of control only upon the reception of a larger number of pulses arriving in a substantially regular and controllable inanner. Since regularity and controllability are not attributes of the usual noise signals, the present invention therefore provides a novel system which is generally free from noise effects and is highly satisfactory in its operation.

Oneobject of the invention, therefore, is to provide a convenient and highly efficient remote control system for radio receivers wherein the usual interconnecting cable or cables are entirely dispensed with.

Another object of the invention is to provide a novel remote control system for a radio receiver wherein volume increase or decrease may be effected simply by producing a train of control impulses consisting of a small number of such impulses, and the receiver may be tuned to a desired signal carrier frequency simply by producing a train of control impulses consisting of a larger number of impulses, there being a common means at the receiver operative in response to the said control impulse trains to effect the said control functions.

Another object of the invention is to provide in such a system novel volume control means by which the degree of control is regulated by the duration of a control pulse, following one or more short pulses which prepare the control meansfor operation in response to the longer pulse.

A further object of the invention is to provide an electro-mechanically controlled radio receiver responsive to control signals from a remote point wherein-certain of the control apparatus, following the termination of a particular control function, is returned to a definite zero or home position whereby the said apparatus is in condition for further actuation upon the reception of a subsequent control signal.

A still further object of the invention is to provide a system of this character which is substantially insensitive to or unaffected by noise pulses regardless of their origin.

These and other objects and novel features of the invention may be clearly understood by reference to the following description and the accompanying drawings.

In the drawings:

Fig. 1 is a diagrammatic illustration of the system;

Fig. 2 is a diagrammatic illustration of the control signal generator;

Fig. 3 is a fragmentary detail view of a control device provided on the impulse sender;

Figs. 4, 4a, 5, 5a, 6 and 6a are illustrations of control signals employed;

Fig. '7 is a detailed illustration of the control apparatus at the receiver; and

Fig. 8 illustrates a specific mechanical embodiment of the stepping mechanism employed in the control apparatus of Fig. 7.

Referring to Fig. 1, there is shown a diagrammatic representation of the system, in which the remotely located control signal generator is shown at I, while the entire apparatus at the radio receiver is shown at 2. The receiver comprises the usual antenna 3, receiver proper 4, and loud speaker 5. A coil 6, by virtue of the mutual inductance existing between it and a coil in the generator I, receives the control signals from the generator and supplies them to an amplifier 1, which in turn supplies the control signals to the control apparatus 8. The latter controls the radio receiver. A power supply unit 9 furnishes the necessary energy for the unit.

The control signal generator Referring now to Fig. 2, the remotely located control signal generator comprises an electric wave generator I in combination with an impulse sender II. The generator may be of any type suitable for conveniently and economically generating small amounts of medium frequency power. For purposes of illustration, there is shown a vacuum tube generator of a type well known in the art. Located in an accessible and convenient position on the out-.

side of the small housing or casing I is the impulse sender II, which may in general resemble the usual type of telephone dial, and which may be of a design similar to that described in United States Patent No. 1,153,951, but including important modifications hereinafter described. The main dial terminals I2 are so connected in the plate circuit of the oscillator tube l3 that plate voltage from source [4 is applied only for a number of equally spaced brief instants, the number depending on the number dialed. The result is a series of pulses, each pulse consisting of a short wave train, preferably of constant amplitude. The coil I is coupled to the coil IE to which there is connected a third coil I! which, as has already been mentioned, is inductively coupled with the coil 6 (Fig. 1) at the radio receiver. Coils i! (Fig. 2) and 6 (Fig. 1) together comprise a simple air core medium-frequency transformer, differing from those used, for example, in the intermediate frequency stages of superheterodyne I receivers largely in the relative sizes and separation of the coils. Thus the coil I! may be looked upon as the primary inductor of such a transformer while the coil 6 is the secondary inductor. This particular part of the system is more fully described and claimed in the copending application of David Grimes, Serial No. 220,364, filed July 20, 1938.

If now, for example, position number 5 is dialed on device ll a series of five equally spaced Wave trains of equal duration will be propagated, as represented in Fig. 4. For the purpose of conserving the energy of the battery I 4 housed within the casing lo, the impulse sender is equipped with auxiliary contacts I8 which are included in the filament circuit of tube 13, and there is provided a circuit-closing mechanism which operates to close these contacts as soon as a dialing operation is begun. As soon as the dial operation is completed, the contacts l8 are again opened. The auxiliary'contacts IS with their associated actuating mechanism are fully described and claimed in the co'pending application of Elmer O.

Thompson, Serial No. 220,368, filed July 20, 1938.

Since this feature forms no part of the present invention, it is unnecessary to illustrate or describe it further herein.

For a purpose to be described later, provision is made on the impulsesender II for manually controlling the duration of the last pulse of a series. This may be accomplished in a simple manner by modifying the device of the abovementioned patent as illustrated in Fig. 3, where- A, in the rotatable dial is shown at [9 and the stationary frame or casing of the device is shown at 20. The peripheral ortion of the dial adjacent the wall 20 is provided with a projection 2| adapted to engage a manually-depressible pin 22 carried by wall 20. When the pin 22 is pressed inward against the action of its spring 23, it is disposed in the path of projection 21 and interrupts the return movement of the dial at the time when contacts [2 are closed to send the last impulse. The pin 22 may be located for convenience adjacent the finger stop of the dial, and the projection should be so located that it engages the pin at the time above mentioned.

This impulse-prolonging mechanism is to be used when positions 2 and 3 are dialed, as

described hereinafter, to effect propagation of the wave trains shown in Figs. 5 and 6. The first impulse of Fig. 5 is of predetermined short duration, while the second impulse is of a duration determined by the length of time pin 22 continues to be depressed by the operator. In the wave trains of Fig. 6, the first two trains are of normal short duration, while the third impulse is of controllable prolonged duration. In experimental models, an average length for these short wave trains or pulses and the spaces between them has been about .05 second which corresponds to a pulse frequency of ten per second.'

In the above-mentioned Thompson application, there is disclosed and claimed a mechanism for controlling the duration of pulses, and that mechanism may be employed instead of the simple device of Fig. 3.

In experimental remote control system utilizing the present invention, it has been found that the frequencies just below the low frequency end of the broadcast band are most suitable. A highly satisfactory model was constructed wherein the signal frequency was variable between the limits of 38.0 and 420 kc., this variation being secured bymeans of the adjustable padder 24 (see Fig. 2). Where two or more remote control systems are to be operated within, say, fifty feet of each other it is important that there be some provision for varying the operating frequencies of the several systems to prevent undesired interaction and interference between the various units. Thus, one might be adjusted to operate at 380kc., another at 383 kc., and so on.

The power supply system 'Reference may now be had to Fig. 7, in which the control'mechanism at the receiver is illustrated. In this figure, only certain parts of the radio receiver are shown, the receiver being of conventional form. For the purpose of amplifying the signals from the remote control unit and for utilizing these signals in the control of a radio receiver, there is located at the receiver a group of amplifiers, relays, switches, and associated circuit elements and mechanisms, as shown in Fig. 7, which will be referred to collectively as the remote control signal amplifier and control apparatus. There is also provided at the receiver a power supply unit for supplying to the amplifier and control apparatus the plurality of voltages which are required in operation. While any suitable power supply system may be employed, the power supply system shown in Fig. '7 will sufiice for the purposes of the present disclosure. The circuit will be clearly understood by those skilled in the art and therefore only a brief description is deemed necessary. Two transformers 25 and 26 are provided. Transformer 25 supplies power to the motorized condenser gang and volume control drive, as will be more fully described herein after. The transformer 26 has separate secondary windings 21, 28 and 29, and is employed as a plate and heater voltage supply source. rectifier comprises two half-wave diodes 30 and 3! so connected that one-half of the rectified output voltage is positive with respect to ground, while the remaining one-half is negative with respect to ground. Thus, point 32 is at a positive potential with respect to ground and, because of the voltage drop in the choke 33, the point 34 is at a slightly lower positive potential with respect to ground. On the other hand, the point 31 is at a negative potential with respect to ground.

A novel switching arrangement comprising switches 38 and 39 renders the system highly flexible in use. With a particular setting of the switches, it is possible to maintain the power supply unit of the remote control system in an operative condition whether the radio receivers power supply 35 is on or off. The switch 38 is ganged with the receivers volume level control means 40 and comprises the usual manually-controlled off-on switch of the radio receiver, and, a will be shown hereinafter, this switch may also be actuated automatically from a distant point by practicing this invention. When the double-throw switch 39is in the right-hand position, the power supply unit of the control system will be turned on and off according as the switch 38 is turned on and 01f. But when the switch 39 is in the left-hand position, the power supply of the control system will remain on irrespective of whether the switch 38 is on or off, and therefore under these circumstances, it will be possible to turn the radio receiver both on and off from a remote point, as described The hereinafter. The switch 38 also controls a signal lamp 4| which is off when the switch is in the right-hand position and on when the switch is not in this position. When the signal lamp is illuminated, it serves as an indication that the remote control system will remain operative regardless of whether the radio receiver is functioning or not. In this condition, it will be possible to turn the receiver off, and then at any later time to again turn it on by remote control. When the signal lamp is dark, it indicates that the remote control systems power supply unit will be turned off when the receiver is turned off. Thus while the receiver and the remote control system could be turned off by remote control, it would be impossible to subsequently turn them on again by remote control. In this latter case, it would be necessary to manually operate the on-oif switch at the receiver before the remote control system could again be used.

When the switch 39 is in the left-hand position, the cathode of one of the remote control signal amplifier tubes is grounded; and closure of the switch 38 likewise grounds the same cathode. The utility of this arrangement will be explained hereinafter.

The remote control signal amplifier The control signals generated by the control signal generator are induced in the secondary inductor, coil 6, associated with the remote control signal amplifier. This apparatus is located at the receiver, preferably in the receiver cabinet, and is therefore at a distance from the remote control unit. The secondary inductor 6 is preferably made in the form of a large coil, and. it may conveniently be located in the base of the receiver console in a horizontal position near the floor where it will not interfere with the usual receiver components. In any event, this coil and the coil H at the remote control unit should be in parallel planes in order to provide the best magnetic coupling. The coil 5 is tuned to th signal frequency of the remote control unit by means of the padding condenser 43. The voltage developed across this condenser is applied to the input grid of the amplifying pentode 44. The amplified output of this pentode is applied through transformer 45 to the input of the next amplifying pentode 45. Similarly the ou put of the pentode 46 is applied through the transformer 4! to the diode anodes A8 and 49 of tube 55. It will be noted that the inter-stage transformers 45 and 41 are tuned by means of adjustable padders 5|, 52, 53 and 5 By means of these padders and the padder for coil 5, the signal amplifier may be tuned to the signal frequency of the remote control unit, thereby excluding interfering off-frequency signals.

The diode anodes 48 and 49 are strapped together and have no initial or delay bias with respect to cathode 56. This diode section is used to rectify or detect the signal appearing across the secondary winding of the transformer il. For a signal of the form shown in Fig. 4:, the rectified output of the diode will have a D. C. component of a shape similar to that illustrated in Fig. 4a. Similarly, for the signal of Fig. 5, there is obtained the rectified output form shown in Fig. 5a, and for the signal of Fig. 6 there is obtained the rectified output shown in Fig. 6a, and so on. The rectified output voltage of the diode is direct coupled to the control grid 5'! of the pentode section of tube 50 by means of the re-" sistor 58, which in combination with the condenser 59, forms a filter that effectively isolates the grid 51 from the signal frequency components present at the diode input.

The amplified output of the pentode section of tube 50 may be direct coupled to the control grid 60 of the amplifying pentode 6| by means of resistor 62. The plate load resistor 63 of the preceding tube 50 may be correctly chosen so as to give the control grid 60 of the tube 6| a correct negative bias with respect to its cathode 64. This cathode is returned to ground through either one or the other or both of the switches 38 and 39. These switches have already been described in connection with the power supply unit. The optimum grid bias for the power amplifier pentode 6| is one which, for the condition of no signal, biases the tube to cut-off or thereabouts. The coupling resistor 62, in combination with the condenser 65 forms a time delay circuit of appreciable time constant, for example, of the order of .03 second. If the output voltage of the pentode section of tube 50 is of the form shown in Fig. 4a, and if the length of the pulses and the spaces between the pulses are each of the order of .05 second, then the voltage appearing on the control grid 60, and in an amplified form, in the output circuit of the pentode 6 I, will not depart radically from that shown in Fig. 4a. The slight departure from the original form which does result will be of the nature of a reduction in slope of the sides of the pulses, and of a few percent reduction in pulse amplitude. The coupling resistor 62 and the condenser 65 constitute a half-pi-section of a low-pass resistance-capacitance filter. The importance of this filter will be fully explained later, after the reasons for its need have been made apparent.

The control apparatus The complete remote control system has now been generally explained up to that point where amplified pulses of direct current, similar to those shown in Figures 4a, 5a, and 6a, may be made to appear in the output circuit of the final control signal amplifier pentode 6|. These amplified pulses are used to control and actuate control apparatus whose function is to perform the desired control operations in response to the pulses generated by the remote control unit. The control apparatus may be considered as comprising the step-by-step switches 66 and 61, the motordriven mechanism 68, and associated elements. The stepping mechanism, which is generally similar to that described in United States Patent No. 1,336,098, is further illustrated in Fig. 8. The common shaft 14, which carries the contact arms 10 and II, also carres a ratchet 16 which is urged by spring 11 counterclockwise, as viewed in Fig. 8, toward the home position. A pawl 18 carried by armature 19 engages and steps the ratchet when the stepping relay coil 69 is energized. The armature 19 is pivoted at 19a and is held in normal position by spring 11a. The pawl 18 is pivotally attached to the armature and is held out of engagement with the ratchet by spring 18a. The lower end of the pawl is bent as illustrated and engages a spring-pressed pin or plunger 18b. The pawl is thus cammed into engagement with the ratchet. A restraining or holding pawl 80 is pivoted at 80a and is held by its spring 8| in tation of the ratchet by pawl 18, it prevents re-' turn of the ratchet by spring Tl. When the homin the case of the step-by-step switch 61, the coning coil 15 is energized, however, the pawl 80, constituting the armature for coil 15, is moved out of engagement with the ratchet.

For each current pulse of sufiicient magnitude through the stepping coil 69, the contact arms 10 and H of the step-by-step switches 66 and 61 will be advanced by one step or position. Thus the first pulse will lift the arms from the zero or home position to position #1, a succeeding pulse will advance the contact arms 10 and H from position #1 to position #2, and so on, up to position #10.

Even though the pulses have an appreciable duration, as do those illustrated in'Fig. 4a, the stepping process occurs as soon as the pulse attains the amplitude necessary to operate the stepping relays. In a particular case, this might occur at of the maximum amplitude. For pulses having a total duration of 0.05 second, this 80% amplitude may obtain within from .01 to .02 second or less after the initiation of the pulse. Thus, for such a case the'length of the pulse is of no interest from the standpoint of the stepping process. The reason for selecting pulse durations and spacing of a length greater than is actually necessary for the operation of the stepping relays is in order to confine the control signals to a definite and reasonably narrow frequency band which may be readily passed by the remote control signal amplifier to the exclusion of undesired signals outside this band. This will be more fully explained hereinafter in connection with the novel means for reducing the effects of noise pulses.

The contact portions of the contact arms 10 and II should be slightly broader than the distance between the spaced stationary contacts. Then as the contact arm moves forward it will engage a succeeding contact before leaving the preceding one. The object of this is to eliminate sparking at the contacts which would otherwise accompany the progression of the contact arms. It will also be noted in the diagram that tacts of positions #1, #2, and #3 are bonded together by means of a bonding ring 12. Similarly the contacts of positions #4 to #10, inclusive, are bonded together by means of a second bonding ring 13, The contact point #1 of step-by-step switch 66 is grounded for reasons which will be hereinafter clarified in connection with a description of the novel means utilized to minimize the effects of noise pulses.

' It will now be seen that, if the stepping coil 69 be energized by a long direct current pulse, such as that illustrated in Fig. 5a., and if it be assumed that the homing coil 15 is energized during and after this long pulse, the homing coil will be unable to effect return of the contactarms I0 and H to their home positions until the stepping coil 69 is deenergized. The reason why this particular action is desired will be explained presently in connection with the volume control action which is provided by the invention.

The homing coil 15 may be energized by virtue of its position in the plate circuit of the triode 82. Normally this triode is biased beyond cutofl, a condition obtained by grounding its cathode and returning its grid through the serially connected resistors 83 and 84 to the point 31 of the power supply unit. This point, as has already been shown, is at a considerable negative potential with respect to ground. Now if the point 85 be grounded, the grid of tube 82 will swing up to ground potential and thereby permit a flow of plate current sufficient to energize the homing coil 1.5. For reasons hereinafter pointed out, it is provided that after the point 85 is grounded, there is an appreciable time lag before the grid itself reaches ground potential, and this time lag or delay is provided by a time delay circuit comprising resistor 83 and condenser 86. In physical embodiments, this time delay has been of the order of 0.30 second. The point 85 may be grounded, in the system illustrated, in either one or both of two ways, Thus, point 85 is grounded whenever the contact arm II of the step-bystep switch 91 is at any one of the positions #1, #2, or #3. Likewise, point 85 is grounded in any condition wherein the serially connected contacts 81 and 89, and 89 and 99 are closed. The former pair of contacts are closed whenever the contact arms I9 and 'II are not in their home' position. This may be readily brought about by causing the shaft I4 to operate the switch contacts 8'! and 98, as diagrammatically illustrated. For example, the switch contacts may be carried by resilient fingers whose resilience tends to open the contacts, and a cam may be arranged on shaft I4 to close the contacts whenever the arms I9 and II are moved from their home position.

Before describing the operation of the control apparatus as a whole, it will be well to briefly examine the motor-driven mechanism 68. The motor BI is of the series-reversible type having oppositely wound field windings 92 and 93. The direction of rotation is, of course, dependent upon which of the two fields is energized. The armature shaft 99 has suflicient end-play to permit of its being forced to the left by spring 95 Whenever the motor is not in operation. In this condition, the contact 89 carried by spring 95 is brought into contact with the stationary contact 99. Since the contact 89 is grounded through the spring 95, it will be seen that when the motor 9| is not in operation, lead 96 will be grounded. But when the motor is energized, the magnetic forces between the field and armature center the motor shaft longitudinally in spite of the opposition of spring 95. The resultant movement of the shaft 94 to theright' opens the contacts 89 and 99. Electric power for the motor is provided by the transformer 25 which is included in the power supply unit. A voltage is supplied from the secondary of this transformer through the lead 91, thence through the contacts 98 and 99 through the lead I99 and thence to the motor armature. The contacts 98 and 99 are normally closed, and are open only when the homing coil I5 is energized. Now since the lower terminal of the secondary o-f transformer 25 is grounded, it is only necessary to ground a side of one or the other of the fields 92 and 93 through lead I9] or I92 in order to energize the motor. And since the leads I9I and I92 are connected with the contact points #2 and #3 of the step-by-step switch 69 it will be seen that the said .leads may be brought to ground potential by causing the contact arm I9 of switch 69 to make contact with relay point #2 or point #3.

The receiver volume control 49; which is shown in the diagram as mechanically linked to the mo tor armature shaft 94 by means of'g'ear-I93 and. pinion I94, is actuated in a direction to increase.

the volume level when the motor is energized over lead IN, and in the 'oppositedirection 'to de-- crease the volume level whenthe motor is en'ergized over lead I92. If the volume-reducing action is continued, the volumew-ill reach its' mini mum level, and finally the-"receiver spower-sup the auxiliary contacts H2 and I I3.

ply switch 39, which is mechanically linked to the volume control means 49, will be opened to thereby deener'gize the receiver. The mechanical link between the receivers volume control means 49 and the on-off switch 38 may be of that type wherein the switch is turned on and ofPby rotation of the volume control means 49. This form of combined on-ofi switch and volume control unit is well known in the art, and further description is considered unnecessary.

Normally the gear I93 meshes with the pinion I94 as shown in the diagram. However, when magnet I95 is energized, the gear I93 is disengaged from the pinion I94 and is engaged with pinion I99 mounted on shaft I91. To this end the extending portion of shaft 94 may be made flexible so that it may bend, and the magnet I95 serves to shiftthe flexible shaft laterally. Of course, any suitable form of shifting mechanism may be used. The shaft I 91 is mechanically. linked to the receivers tuning condenser gang I 98. The magnet I 95 may be energized from the motor supply transformer 25 Whenever the contact arm II grounds the bonding ring I3. This occurs for positions #4 to #10 inclusive of the switch 61; In order that the magnet I95 may be energized for these positions,'it is, of course, necessary that the contacts '98 and 99 be closed, for these contacts, connected in par allel with contacts I09 and H9, are included in the supply circuit from the transformer 25. The resistor III is connected across the terminals of these contacts merely to reduce sparking, and does not of itself have a sufliciently low impedance to permit operation of the motor 9I or energization of the magnet I95. Closure of contacts I99 and I I9 alone cannot produce sustained energization of magnet I95, for once this magnet is energized the said contacts are opened. This would result in a continuous opening and closing of the contacts I99 and H9 were it not for the fact that contacts 98 and 99 are always closed when the magnet I95 is energized. Mechanically ganged to contacts I99 and H9 are 9 Contact H2 is grounded, while contact H3 is connected with one or more of the cathodes of the tubes in the radio receiver (not illustrated). Thus, when the contacts 'I I2 and H3 are closed, the receiver operates normally, but when these contacts are open some of the receivers cathode circuits will be open and the receiver ceases to, function. The ganging arrangement is such that the contacts H2 and H3 open and close in unison with the contacts I99 and'II9. ,The contacts H2 and H3 therefore perform the function of muting the receiver during remotely controlled station changes.

Mechanically mounted on the shaft I9! is the split commutator I I4 comprising conductive segments H5 and I Ifielectrically insulated from each other. Such devices are well known in the art. Making sliding contact with the segments I I5 and H6 are the commutator brushes 20, 3c, 4c, etc., connected, respectively, to contacts #2, #3, #4, etc. of stepping relay 66. It will be noted that brush-es 2c and 3c are diametrically opposite one another, while the other brushes are spaced along the periphery of the commutator in a semicircle. For simplicity of illustration some of the brushes and their connections are omitted. The brushes 2c and 3c are also connected to the motor field leads IN and I92, respectively.

It will now be seen that when the arm I9 engages any one of the contacts #4 to #10, unlessthe corresponding brush happens to be in engagement with the insulating portion of the commutator, the motor 9| will be operated through one or the other of its field windings to rotate the commutator until the insulating portion thereof interrupts the connection. When the motor is energized through brush 2c and field winding 92, it rotates the commutator clockwise, as viewed in Fig. 7. When the motor is energized through brush 3c and field Winding 93, it rotates the commutator counterclockwise. Thus, it will be seen that the commutator is rotatable through an are which maybe slightly less than 180 depending of course upon the disposition of the brushes, and the tuning condenser I08 may be rotated accordingly. Each of the brushes other than 2c and 30 corresponds to a station to which the receiver may be tuned, and the brushes are preferably adjustable to permit preselection of a certain group of stations.

From the foregoing description, it will be apparent that when the arms 10 and H are moved to either position #2 or #3, the motor 9| drives the volume control means 40 to increase or decrease the volume level, and when the arms are moved to any one of the positions #4 to #10, the motor drives the tuning condenser I08 and the commutator H4 to adjust the condenser settin so as to tune the receiver to the station corresponding to the selected position.

The normal operation of the control apparatus as a whole may be most clearly and concisely explained by outlining the various circuit element actions and changes which occur in response to representative series of pulses. In the first tabulation below, there is assumed the arrival, in the stepping coil 69, of a series of pulses such as is illustrated in Fig. 4a. In Fig. 4a, these five pulses are designated A to E in elusive, and they are so referred to in the following table:

Position of stepby-step switches Contacts open Pulse NIL Explanatory remarks 87-88 This is the normal position oi the contacts before the first pulse A has arrived; this position of contacts is shown in the diagram of Fig. 7.

Contacts 87-88 close as soon as the ganged contact arms 70 and 71 of the switches 66 and 67 leave their home position. With contacts 87-88 closed and bonding ring 72 grounded, the negative bias on the grid of triode 82 begins to leak oil to ground, but because of time delay circuit 83-86 this occurs so slowly that the contact arm 71 leaves the contact points bonded by ring 72 before the homing coil 75 is energized.

When contact #2 is reached, the motor 91 is energized the contact arm 70 will arrive at its ultimate contact point 111 this case) so quickly that this preliminary rotation of the motor is of no consequence except in so far as it causes the contacts 89-90 to open.

No changes from above state.

Same Same and it begins to rotate the shaft 94. However,-

Contacts open Explanatory remarks As the contact arm 71 leaves the contacts bonded by ring 72, the grid of the triode 82 is again allowed to [all well below ground potential. When the arm 71 reaches the contacts bonded by ring 73, the magnet 105 is energized from the secondary of transformer 25. This causes the ganged contacts 109-110 and 112-113 to open, the latter muting the radio receiver; simultaneously the energized magnet 105 operates magnetically to uncouple the motor from the receivers volume control means 40 and to couple the motor to the receivers condenser gang 108 by means of shaft 107.

As the last pulse arrives, the cpntact arms stop at position #5, and t e motor turns the split commutator until the circuit is opened upon the arrival of 50 at the insulating portion of the commutator periphery.

Same Same When the motor stops, contacts 89-90 close, grounding the grid of triode 82 through rcsistor 83. Within, say, 0.15 second, the charge on the grid has leaked ofi sufficiently to permit energization of the homing coil with attendant opening of contacts 98-99, and homing oi the contact arms 70 and 71. At the same time, since the contacts 98-99 and 109-110 are now both open, the magnet is deenergized which removes the motor drive from the shaft 107 and recouples the motor to the receivers volume control means 40.

Simultaneously with the deenergization of magnet 105, the ganged contacts 109-110 and 112-113 are reclosed, the closing of muting contacts 112-113 permitting the radio receiver to operate normally.

While the above table assumes the arrival of the five pulses of Fig. 411, it will be understood that the actions therein outlined are similar to those which would occur for 4, -6, 7, 8, 9, or 10 pulses. Between these limits a difierent series of pulses results only in causing the split commutator H4 to stop at a dififerent point, depending on which of the brushes 40 to I00, inclusive, is grounded by the final position of contact arm 70. Thus the above tabulation is in general illustrative of the actions which obtain in remotely controlled station selection.

When only two or three pulses occur in the stepping coil 69, such as those illustrated in Figs. a and 6a, a somewhat different situation results. The following table is based upon the arrival of two pulses such as shown in Fig. 5a, that is, a short pulse A followed by a longer pulse B. The table is, in general, illustrative of the novel method and means provided herein for the control of volume, which constitutes a highly important part of this invention.

Position of stepby-step switches Contacts open Pulse Na Explanatory remarks (Fig. 5a)

This is the normal position of the contacts, before the first pulse A, has arrived, as shown in the diagram.

When the contact #2 is reached, the motor 91 is energized and rotation of shaft 94, gear 103, and pinion 104 results. This produces a progressive change in the receivers volume control means 40 resulting in increased volume level. Contacts 89-90 open as soon as the motor 94'is energized.

After the pulse B has persisted for, say, 0.2 second, the grid of the triode 82 has reached a potential so close to ground potenti that the homingcoil 75 is energized, and contacts 98-99 are opened. The opening of these contacts is of no interest in the volume control operations, however, for the contacts 109-110 remain closed, and since the contacts 98-99 and 109-110 are in parallel, the opening of contacts 98-99 can produce no effect while contacts 109-110 are closed. Although the homing coil 75 is now energized, it cannot as has already been explained, return the contact arms 70 and 71 to their home positions while the pulse B persists, and thus the increase in volume level continues for the duration of the pulse B, or until the volume control means 40 reaches its maximum extent. The mechanical drive for the volume control means may include some friction drive means, as for example, a belt and pulleys, so that if the motor 91 continues to run after this position is reached no damage will result. When the pulse B 'ceases, the stepping coil 69 is deenergized, and the contact arms are returned'to their home or zero position.j

Position Con- Conil tacts tacts Explanatory remarks (Fig. 5a) switches 059d 0 87-88 89-90 Contacts 87-88 open when 98-99 the contact arms reach 109-110 their home position. 112-113 Contacts 89-90 close as soon as the motor is deenergized, and contacts 98-99 close as soon as the homing coil is deenergized which occurs shortly after contacts 87- 88 open.

For a series of three pulses as illustrated in Fig. 6a, the actions would be similar to those tabulated above for two pulses, except that in the case of three pulses of Fig. 6a the positions #1 and #2 are reached as a result of pulses A and B, while position #3 is reached as a result of the institution of the long pulse C. The motor 9| is caused to turn in a direction which produces a volume level decrease, and finally turns off the receiver completely.

It will now be appreciated that the choice of time constant of the time delay circuit B3-86 which delays homing action is of considerable importance. vIf this delay were not present, then homing would occur immediately following the first pulse due to grounding of the bonding ring 12 and the point 85, and the contact arms 8 and H would be immediately returned to their home positions before they could the advanced another step. It is therefore necessary that the time constant of the circuit B38-'5 be at least of such a magnitude that-the contact arm ll be enabled to pass position #3 before the homing coil 15 becomes energized. Once the position #3 is passed, the bonding ring 13, and hence point 85, is no longer at ground potential, and danger of premature homing no longer exists.

In connection with the system of stepping and homing incorporated in this invention there is encountered an unusual problem; this occurs only when both the receiver and power supply unit are turned off by remote control. Assume that the contact arms are at positions #3 and that the motor 9| is operating to turn the receiver and power supply unit off. The homing coil15rwill be energized, but cannot home the contact armsas long as the stepping coil 69 is energized. At the instant the switch 38 is opened, all circuits in the receiver and in the remote control system become deenergized in unison. The result is that the homing coil 15 is unable to home the contact arms 10 and H which would therefore remain at the position #3, the position for volume decrease or for turning off the receiver. Now if later the switch 30 were closed manually, thus energizing both the receiver and the remote control system power supply unit, the motor 9| would promptly operate to again open the switch 38, and thus it would be impossible to place the receiver in an operating condition. To avoid this, .the invention provides means whereby the homing of the contact arms 10 and H may take place'even after the switch 38 is opened. It will be well understood by those skilled in the art that the filter condensers H1, H8, H9 and I20, associated with the remote control systems power supply unit, may retain a residual charge for a short time after the power input to the unit has been cut off. It is therefore'provided in'a'ccordance with the invention, that the circuit of the stepping coil 69 be opened coincident with the opening of the switch 38. Thus when the switch 38 is opened, the stepping coil 69 will become deenergized at once, but the homing coil 75 will continue to function for a'short time thereafter by virtue of the residual charge existing in-the filter condensers H1 and H8. For step-by-step switch of the type described, this short time is sufiicient for the homing of contact arms 10 and H to occur. In the particular embodiment of the invention shown in Fig. 7, the circuit of the stepping coil 69 is opened by means of the switch 38. One arm of the switch is connected between the oathode of the tube BI and ground. Opening of the switch therefore breaks the load circuit of the tube 6| and the stepping coil 69 is thereby de-- energized.

For remote control operation with the switch 39 thrown to the left-hand position, i. e., where the remote control systems power supply unit remains energized whether the receiver is on or off, it is neither permissible nor necessary that the load circuit of the tube 6| be opened as in the case just described. Therefore it is provided that the lower arm of switch 38 be shunted by the lower arm of switch 39, and thus for this mode of operationthe cathode of the tube 6| will remain grounded regardless of the position of switch 38.

Operation of the complete system The functions, construction, and operation of the several units, which under normal operating conditions comprise all the necessary components of the complete remote control system, have now been completely described; but before describing the novel means provided by this invention to render the system immune to noise disturbances, it will be well to trace briefiy a few typical operations of the complete system. Assume to begin with that the radio receiver is turned off, but that the power supply associated with the remote control signal amplifier is on. The radio receiver may then be turned on as follows: Referring first to the remote control unit I, the pin or plunger 22 is depressed, and position #2 is dialed on the dial II. There are then produced in the tuned circuit l5-24 and the associated primary inductor I1 oscillating currents of the form shown in Fig. 5. Similar signals are induced in the secondary inductor 6 of the remote control signal amplifier, amplified by the radio frequency amplifier comprising tubes 44 and 46, and rectified by the diode section of the multi-purpose tube 50. The rectified signals will be similar to those shown in Fig. 5a. These signals are amplified by two directcoupled amplifier stages which include the amplifier section of the tube 50, and the power amplifier tube 6|. The appearance of the two pulses in the stepping coil 69 raises the ganged contact arms 10 and H to position #2 whereupon the motor 91 is energized and caused to rotate in that direction which tends to turn the volume control means 40 away from its original minimum position. Now, since the radio receivers off-on switch 38 is mechanically linked to the volume control means, it follows that the first few degrees of turn imparted to the volume control will place the switch 38 in its on position. Continued operation of the volume control means will ensue until the plunger 22 is released.

The dial positions #4 to #10 inclusive represent seven different radio stations, and any one of these may be automatically tuned in by dialing the corresponding number. Assume that a desired station corresponds to position #5 and that this position is dialed. In the tuned circuit l5-24 there will then appear currents of the form shown in Fig. 4, and, as before, these signals will be induced in the coil 6, amplified, rectified, and further amplified, the resulting signals being of the form'shown in Fig. 4a. In a manner already explained the contact arms 10 and H of the step-by-step switches 66 and 61 will be advanced to positions #5. During this stepping process the magnetic gear shift arrangement including magnet I05 will have coupled the motor 9| to the shaft I01. Thus rotation of the split commutator H4 will result, continuing until the grounded brush 50 reaches the insulation section of the commutators periphery at which time the desired station will be received.

The receiver may be turned off by depressing the plunger 22 and dialing the third position on the dial II which, in the remote control signal amplifier, gives rise to a rectified signal of the form shown in Fig. 6a. Operation is similar to that outlined for turning the receiver on, except that the receivers volume control is turned toward its minimum volume level position, and in the final few degrees of its rotation the associated on-off switch 38 is turned to its off position.

The means just described for the remote control of volume becomes of particular interest when the broad underlying principles are examined. The operation is briefly this: The signals utilized for volume level changes comprise, as has already been shown, one or more short pulses followed by a longer control pulse. The short pulses and the first portion of the long pulse serve to set up or re-arranged the circuits of the control apparatus in such a manner that the subsequent operation of the motor will produce a change in the desired direction. Shortly after the institution of the long" pulse, and directly upon the completion of the said circuit re-arrangements, the motor operates to produce the desired change, i. e., Volume level increase or decrease, and the amount of the control or volume level change is dependent then only upon the length of the long pulse. Of economic importance is the fact that these volume control functions are made possible with virtually no greater expense or outlay of equipmnt than if the remote control system were designed for the station changing function only.

It is to be noted that in control of the radio receiver from the remote point for volume increase, volume decrease, or station changes, the completion of the particular operation is followed, within a fraction of a second, by the return of all relays and eleotro-mechanically operated contacts and clutches to the normal positions 1 shown in Fig. '7.

The procedure to be employed in originally setting up the equipment for an assortment ofdesirable stations which may thereafter be automatically tuned in from a remote point is as follows: First, the radio receiver is manually tuned seven. Positions #4 to #10 inclusive on the dial H may be given the station call letter designations rather than numbers. Position #2 mightbe designated as on-loud, and position #3 may be designated off-sof Means for protecting the stepping relay from noise pulses In remote control systems of the type described, the matter of protecting the stepping relays from noise pulses is a highly important consideration. It will be appreciated that the stepping coil 69 cannot itself distinguish between a pulse originating in the control signal generator and a noise pulse of greater or comparable magnitude originating, for example, as a result of atmospheric or electrical power circuit disturbances. It has, in fact, been found that, in systems incorporating no noise protection means, it is possible to tune in any one of the preselected stations by the simple process of rapidly turning on and off an electric light switch or power circuit, ringing a door bell, etc. Thus, for example, eight noise pulses produced by turning an electric light switch on and off four times would cause the receiver to be automatically tuned to thestation corresponding to position #8 of the dial. Such a situation would, of course, be exceedingly annoying, for almost any random series of noise pulses. might readily retune a receiver at a time when such control would be most unwelcome. The intermittent arrival of noise pulses, say by twos or threes, might result in volume changes which, While individually small, would in time produce large undesired volume changes, and might even turn the receiver off if continued for any appreciable time. Therefore the provision of means for greatly minimizing the magnitude of noise pulses and their effects, as hereinafter to be described, constitutes one of the important features of this invention.

The first means for securing a reduction in noise level is incorporated in the remote control signal amplifier and resides in the sharply tuned radio frequency amplifier which includes the tuned secondary inductor 6 and the tuned interstage transformers 45 and 41. sharply peaked, the transformer coupling being in each case below critical coupling. In addition to discriminating against random noise pulses, the tuned amplifier also affords sufiicient selectivity, to permit several of these remote control systems to be operated within the same area but at different frequencies. This has already been mentioned.

The second means of securing noise reduction resides in a low-pass filter, already briefly referred to in connection with the description of the remote control signal amplifier- It is located between the double diode pentode tube 5.0 and the power amplifier pentode 6|. The series element is the coupling resistor 62, while the shunt element is provided by the condenser 65. It is a function of this resistance-capacitance filter to pass, without too serious attenuation, control pulses of the forms illustrated in Figs. 4a, 5a, and 6a. Where the minimum duration of The amplifier is the short pulses and the spaces between them is of the order of 0.05 second, the time constant of the filter may be of a slightly smaller order. In

a physical embodiment the time constant wasv of noise pulses set up by commutator type motors,

high speed circuit-interrupting vibrators and the like, will be very materially discriminated against because of their high pulse frequencies. It follows, therefore, that a low-pass filter is a highly effective single means for guarding against ran dom actuation of the stepping relay by undesired signals having pulse frequencies appreciably greater than those of the desired control signals.

There still remain to be considered methods for discriminating against noise signals having pulse frequencies below the pulse frequency of the desired control signals. Noise signals of this type might be generated, for example, by slowly turning on and off various household light or power circuits, or by turning on or off several such circuits in succession. Complete protection against these signals is afforded by the triode 82 in combination with the homing coil 15 and step-by-step switch 61 the normal functions of which have already been described in connection with the control apparatus. It will be recalled that, for the positions #1, #2, and #3 of the contact arm H, the point in the grid circuit of the triode 82 is grounded, permitting the negative charge on the grid to slowly leak off to ground through the resistor 83 at a rate dependent upon the magnitude of the time constant of the circuit 83-86. It will be further recalled that when the grid has fallen practically to ground potential, the homing coil 15 is thereby energized. Now, in order to prevent premature homing of the contact arms 10 and H it is provided that the time constant be of such a magnitude that the homing coil will not be energized until the point 85 has been grounded for a length of time slightly in excess of that normally taken for the contact arm H to completely pass over the positions #1, #2, and #3. For pulses of the frequency and form shown in Fig. 4a, this time. is approximately 0.3 second, and therefore for such signals the time constant of the circuit 8386. might Well be adjusted to permit energization of the homing coil 15 only after the point 85 has been grounded for, say, 0.35 second. It follows then that, if a series of noise pulses are received whose pulse frequency is so low that the positions #1, #2 and #3 are not traversed within 0.35 second, the homing coil 15 will operate to return the contact arms 10' and H to their home position before any one of the station-selecting positions, #4 to #10 inclusive, has been reached. It also follows that, where the time between peaks of the undesired noise pulses is 0.35 second or more, the contact arms 10 and II will be returned to their home position before succeeding pulses arrive, and thus the contact arms will be merely advanced repeatedly to position #1, but no further. This means of protection against noise signals of low pulse frequency, comprising the triode v82, homapparatus, that the stepping coil 69 remains energized for the duration of any pulse, and that while so energizedthe homing coil 15 is prevented from homing the contact arms even though the homing coil be energized at the time. The combination of an electrical low-pass filter followed by an electro mechanical high-pass filter results in a band-pass filter which discriminates markedly against pulse frequencies which differ appreciably from the pulsefrequency of the desired control signals. This band-pass filter results in a discriminatory combination which would be difficult to equal by any other means of comparable simplicity.

There remains one further important class of interfering signal, namely, rectified signal noise pulses having a duration comparable to, or greater than those shown in Fig. 4a. Single pulses of this nature are not discriminated against by any of the circuit elements so far described. The effect of such single pulses is to raise the contact arms from their home position to position #1, and to hold the arms in that position for the duration of the pulse, after which the arm is returned to its'home position by means of the homing coil. Now if, for example, point #1 on the step-by-step switch 66 were the position for volume level increase, and if a long noise pulse were received, then the contact arms I and 1| would be raised to that position and the volume level of the receiver would be raised to an extent depending on the length of the noise pulse. Successive widely spaced long pulses would successively raise the contact arms to position #1 and cause continued volume level increase up to the limit of the radio receivers volume control means. In order to circumvent these difliculties, position #1 of the step-by-step switch 66 is made blank, or is grounded, as shown in the diagram of Fig. '7. With this arrangement successive widely spaced noise pulses of the type described will merely raise the contact arm to this blank or dead position and the radio receivers control circuits will not be affected in anyway. If there be insufiicient time between the long pulses to permit homing, the contact arms will merely remain at the blank position until the disturbances abate. Under this system the only way that the contact arms could be made to arrive at position #2, and thus produce a volume increase, would be for the noise pulses to arrive in correct sequence and to be of the proper duration, 1. e., first a short pulse to raise the contact arms to position #1, followed at the correct time interval, by a longer pulse. It should be noted that if the first pulse is not short, the grid of tube 82 will have had time to fall to ground potential, thus causing energization of the homing coil, which will result in homing of the contact arms at the end of the pulse. If the interval between the pulses is too short, the rather large time constant associated with the input of the tube 6| will not enable the amplifier to difierentiate between the pulses, and its output will be simply one long pulse. On the other hand, if the interval is too long, the homing coil 15 will act to return the contact arms to their home position during this time. This discrimination as to the length of the intervals between pulses, is, of course, due to the band-pass effect which has already been described. As is to be expected, it will be exceedingly rare in nature, or in random manmade interferences, for a short pulse to be followed at exactly the correct interval by a long pulse. Similarly, in order that the noise pulses be enabled to reduce the volume, or to turn the receiver off, it would be necessary that wo sho t pulses be followed by a long pulse, all correctly spaced. This is an even more improbable occurrence than that one previously mentioned. In much the same way, it would be highly unlikely for a certain larger number of equal and cor rectly spaced noise pulses to arrive and thereby cause the receiver to automatically tune to a difierent station. Thus, the provision of a blank first position on switch 66 removes virtually all difficulty from long noise pulses regardless of their spacing, and from short pulses incorrectly spaced, or from combinations thereof.

A further protection against noise pulses will now be described. It has already been shown that a convenient location for the control amplifiers secondary inductor, coil 6, is the base of the receiver console or cabinet. In this position the coil will normally be in close proximity to the power suppyl cord, as shown in Fig. '7. It was found that a great deal of the noise pick-up of the coil 6 is directly from the power supply cord. This is particularly true of disturbances arising within the building which houses the receiver. Especially severe in this respect are disturbances occasioned by the opening or closing of the varion -power, light, or heating circuits, or the operation of motors, or other apparatu having contacts at which sparking occurs. While it has been shown that these noises may be rendered generally harmless by the use of a dead first position on the step-by-step switch 66 it is nevertheless, of interest to reduce by as much as possible the amount and severity of noise reaching the remote control amplifier. For example, strong interfering noise signals of a more or less continuous nature could either partially or completely mask a desired series of control impulses, and as a result, although the interference itself could not operate the receivers tuning circuits, the operator would be forced to wait until the disturbance abated before dialing could be successfully accomplished. Modern radio receivers are, of course, generally provided with line filters associated with their power supply, or they may be provided with power transformers whose windings are mutually shielded electrostatically, and it is well known that these are efiective means for preventing power circuit noises from entering the receiver circuits by way of the power line; but these means do not prevent pick-up of noise from the power supply lead by such coils as might be used in this form of remote control. It is therefore an important feature of this invention that an auxiliary filter be located at the power outlet fixture into which the receivers supply cord is plugged. The filter, which in its simplest form may be a condenser [2| shunted across the line, may conveniently be built into the housing of the supply cord plug. Thus, the cord which supplies the receiver with power is now efiectively isolated from power line disturbances, whether they arise from outside sources, or from causes Within the receiver itself. With this treatment it has been found that the total noise pick-up of the coil 6 is very considerably reduced.

To recapitulate, there have now been described five separate means for discriminatin against undesired signals and noise pulses, to wit-a sharply tuned radio frequency amplifier, an electrical low-pass filter, an electro-mechanical highpass filter, the use of a dead first position on the step-by-step switch, and finally the use of a power cord which is isolated from radio frequency by suitable filtering at both ends. When all of these means are incorporated into a remote control sysdrawings, it will be understood that the invention.

is capable of various forms of physical expression, particularly in respect to the structural details. Moreover while in the preferred form of the invention a purely inductive coupling i provided between the primary inductor of the control signal generator and the secondary inductor at the radio receiver, it is entirely feasible to employ a radio link between the radio receiver and the remote point in which case the coils would have to be designed to operate as antennae capable of efliciently radiating and receiving electro-magnetic waves. The invention is therefore not to be limited by the specific disclosure but only by the scope of the appended claims.

Iclaim:

1. In a control system for a radio receiver or the like, means for generating a train of signal impulses of substantially equal duration, means for generating a train of impulses of .unequal duration, and common means at the receiver responsive to said first-mentioned impulse train for tuning the receiver to a desired intelligence signal, and responsive to said last-mentioned impulse train for varying the volume level of the intelligence signal being reproduced by the receiver.

2. In a control system for a radio receiver or the like, means for generating a train of signal impulses of substantitally equal fixed duration, means for generating a train of impulses comprising at least one impulse of fixed duration and a subsequent impulse of controllable duration, and common step-by-step switching means at the receiver responsive to said first-mentioned impulse train for effecting a control function, and responsive to said last-mentioned impulse train for effecting a different control function,

3. In a control system for a radio receiver having a volume control device, a single means for generating a train of control impulses comprising at least one impulse of fixed duration and an impulse of controllable duration, and means for operating said control device in a direction dependent upon the total number of said impulses and to an extent dependent upon the duration of said controllable impulse.

4*. In a control system for a radio receiver having a gain control device, the provision of controllable driving means coupled to said gain control device for effecting change in the output volume level of said receiver, means for generating a train of control impulses comprising at least one impulse of fixed duration and a following impulse of controllable duration, a step-bystep switch at said receiver for determining in response to the total number of said fixed and said controllable pulses the direction of said volume level change, said switch being responsive to the duration of said following controllable pulse for controlling the extent of said volume level change.

5. In a control system for a radio receiver having a gain control device, the provision of con.- trollable driving means coupled to said gain control device for effecting change in. the output volume level of said receiver, means for generating a train of control impulses comprising at least one impulse of fixed duration and a following impulse of. controllable. duration, means including, a stepping mechanism at said receiver for actuating said controlloble means in response to said control impulses, said stepping mechanism being. responsive to the duration of said controllable impulse for controlling the magnitude of the change in the volume level, and means for homing said stepping mechanism after a predetermined, time following the initiation of said impulses,

6. In a control system for a radio receiver having a volume control device, means at the receiver for operatingsaid device so as to increase or decrease the volume level, said means including a step-by-stepdevice having a home position and a plurality of selectable operating positions, means urging said step-by-step device to its home position, means for generating a train of control impulses comprising at least one impulse of fixed duration and a subsequent impulse of controllable duration, stepping means responsive to the number of said impulses for operating said step-by-step device to effect a volume increase or decrease and for controlling the extent of the volume variation according to the duration of said controllable impulse, and means for returning said step-by-step device to home position after a predetermined time interval following the initiation of said impulses, said stepping means preventing return of the step-by-step de-.

vice to home position if said interval terminates within the duration of said controllable impulse.

7. In a control system for a radio receiver having a volume control device, a reversible motor for operating said device to increase or decrease the volume level, control means for said motor including a step-by-step switch having a home position and a plurality of selectable operating positions, means urging said switch to home position, means for generating a train of control impulses comprising at least one impulse of fixed duration and a subsequent impulse of. controllable duration, stepping means responsive to the number of said impulses for operating said motor in a desired direction and for a time dependent upon the duration of said controllable impulse, and means for returning said switch to home position after a predetermined time interval following the initiation of said impulses, said stepping means preventing the return of said switch to home position if said interval terminates within the duration of said controllable impulse.

8. In a control system for a radio receiver or the like, means for generating a train of signal impulses of substantially equal duration, means at the radio receiver responsive to said impul e train for effectin a control function, and additional means at said receiver responsive to an intermediate one of said signal impulses for effecting muting of said receiver.

9. In a control system for a radio receiver or the like, means for generating a train of signal impulses of substantially equal duration, means at the radio receiver responsive to said impulse train for effecting a control function, and means at said receiver responsive to a predetermined one of said impulses for effecting muting of said receiver following the said impulse and during subsequent impulses of said train.

10. In a control system for a radio receiver or thelike, means for generating a train of signal impulses of substantially equal duration, means at the radio receiver responsive to said impulse train for effecting a control function, additional means at said receiver responsive to an intermediate one of said signal impulses for effecting muting of said receiver, and means for prolonging the muting of the receiver for a predetermined time interval after the last impulse of said train.

11. In a control system for a radio receiver or the like, means for generating a train of signal impulses of substantially equal duration, means at the radio receiver responsive to said impulse train for effecting a control function, means at said receiver responsive to a predetermined one of said impulses for eifecting muting of said receiver following the said impulse and during subsequent impulses of said train, and means for prolonging the muting of the receiver for a predetermined time interval after the last impulse of said train.

12. In a remote control system for radio receivers and the like, means for generating atrain of control impulse signals, inductive means located at the radio receiver for deriving said control signals from said generator, a power supply cable in proximity to said inductive means for supplying said radio receiver with electrical power from an available power source, whereby disturbance signals tend to be induced in said inductive means and interfere with the remote control of said radio receiver, filter means at the receiver connected to said cable, and additional filter means disposed near the juncture of said cable and said power source for preventing said disturbance signals from entering said cable and causin interference in said inductive means.

13. In a remote control system, apparatus to be controlled located at a firs-t point, apparatus at a second and remote point for controlling said first-mentioned apparatus, means at said second point for generating an electrical wave, means for keying said wave generator to produce a number of short pulses of predetermined duration, auxiliary means associated with said keying means for keying said generator to produce short pulses followed by a longer pulse of controllable duration, a step-by-step switching means at said first point having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the number of said short and long pulses for advancing said switch arm to a corresponding one of said operating positions, means associated with some of said operating positions for effecting a control function, and means associated with other of said operating positions for effecting a different control function, the magnitude of said last-named control being a function of the duration of said longer pulse.

14. In a control system for a radio receiver or the like, means at a control point remote from said receiver for generating an electrical wave, means for keying said wave generator to produce a number of short pulses of predetermined duration, auxiliary means associated with said keying means for keying said generator to produce short pulses followed by a longer pulse of controllable duration, a step-by-step switching means at said receiver having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the number of said short and long pulses for advancing said switch arm to a corresponding one of said operating positions, means associated with some of said operating positions for effecting the tuning of said receiver, and means associated with other of said positions for efiecting control of volume level, the

pulse of manually-controllable duration, a step by-step switching means at said receiver having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the total number of said pulses for advancing said switch arm to a corresponding one of said operating positions, means associated with some of said operating positions for effecting the tun- I ing of said receiver in response to control signals comprising only short pulses, and means asso-- ciated with other of said positions for effecting changes in volume level in response to control signals comprising both short pulses and a longer pulse, the extent of said volume level change being a function of the duration of said longer pulse.

16. In a control system for a radio receiver,

stepby-'step switch means at said receiver com-' prising a pair of movable arms and stationary contacts associated respectively with said arms, means controlled by one of said arms and its associated contacts for changing the tuning of said receiver, meanscontrolled by the other arm and its associated contacts for muting said receiver, and means for actuating said arms in unison, to' thereby tune said receiver to a desired station and to render the receiver inoperative during tuning thereof.

17. In a control system for a radio receiver, step-by-step switch means at said receiver comprising a pair of rotatable arms and stationary contacts associated respectively with said arms, means controlled by one of said arms and its associated contacts for changing the tuning of said receiver, means controlled by the other arm and its associated contacts for muting said receiver, means for generating a plurality of control signal impulses, and means responsive to said signal impulses for actuating said arms in unison, to thereby tune said receiver to a desired station and to render the receiver inoperative during tuning thereof.

18. In a control system for a radio receiver,

step-by-step switch means at said receiver comprising a pair of rotatable arms and stationary contacts associated respectively with said arms, means controlled by one of said arms and some of its associated contacts for varying the volume level of said receiver, means controlled by said one arm and other of its associated contacts for changing the tuning of said receiver, means controlled by the other arm and its associated contacts for muting said receiver, means for generating a plurality of control signal impulses, and means responsive to said signal impulses for actuating said arms in unison, to thereby vary the volume level of the receiver or tune the same to 1 a desired station, the said contacts associated with said other arm for muting the receiver being arranged for engagement by the said arm coincident with the tuning of the receiver. I 19. In combination with a radio receiver having a tuning shaft and a volume varying means,

a motor coupled to said tuning shaft, a plurality of energizing circuits for said motor, a plurality of control circuits for said volume varying means, a controller in each energizing circuit to dee'nergize said motor in response to movement of said shaft to predetermined positions, a step-by-step switch having a neutral position and a plurality of successive circuit closing positions, means responsive to a plurality of successive impulses to move said switch from neutral position to certain successive positionsin which it closes successive control circuits and to other successive positions in which it closes successive energizing circuits, a delayed circuit control means having a predetermined time constant, reset means under the control of said delayed means to move said switch to neutral position, and means'responsive to the energization of said motor to control the effectiveness of said delayed means, whereby a reset operation is prevented until said motor has been deenergized. A 1

20. In a control system for a radio receiver or the like, means for generating a train of. signalimpulses of substantially equal duration, means for generating another signal including an impulse of controllable duration, and com: mon means at the receiver responsive to said first-mentioned impulses for tuning the receiver to a desired intelligence signal, and responsive to-said other signal for varying the volume level ofthe intelligence being reproduced by the receiver. I

21. In a control system for a radio receiver or the like, means for generating a train 'of control impulses of substantially equal fixed duration and having predetermined frequency characteristics, means for generating another control signal including an impulse of controllable duration, said last-mentioned signal having frequency characteristics identical to those of said train of impulses; said impulses diifering only'in' the duration of said controllable'impulse, means at the receiver responsive to said first-mentioned impulses for tuning the receiver to a desired'intelligence signal, and means'at the receiver responsive to said controllable impulse:

for varying the volume level of the intelligence signal being reproduced by the receiver;

22. In a remote controlsystem, apparatus to be controlled located at a firstpoint, apparatus at a'second-and-remot'e' point for controlling said first-mentioned apparatus, means at said second point for generating an electrical wave, means for keying said wave generator 'to produce anumber of short pulses of p re'determin'ed duration,1 auxiliary means associated withsaidkey ingmeans for producing a longer pulse of controllable duration, a step-by-step' switchingmeans at said first point havingamovable switch arm and aplurality of'select'able operating positions, positioning means responsive to the total number of generated pulses for advancing'said switch arm to a corresponding one' of said oper-" ating' positions, means associated with some I of said operating positions for effecting a'control function, and means associated withother of said operating positions for effecting 'a diiierent control-function, the magnitude of 'sa'id'la'st named control being a function of the duration of saidlonger pulse.

23. ha control-system for a 'radio' receiver or the like, means ata control point remot'efrom said receiver for generatingan electrical wave, means forkeying said wave generator to produce ajnumber ofshort pulses of predetermined.

duration, auxiliary means associated with saidfifi keying means for producing a longer pulse of controllable duration, a step-by-step switching means at said receiver having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the total number of generated pulses for advancing said switch arm to a corresponding one of said operating positions, means associated with some of said operating positions for efiecting the tuning of said receiver, and means associated with other of said positions for effecting control of volume, the extent-of said last-named control being a function of the duration of said longer pulse. r

24. In a control system for a radio receiver or the'1ike,means at a control point remote from said receiver for generating an electrical Wave, means for keying said wave-generator to form a control signal comprising a number of short pulses of predetermined duration, auxiliary means associated withsa'id keying means for keying said generator to form a control signal including a'longer pulse of manually controllable duration, a step-'by step' switching means at said receiver having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the total numberof said pulses for advancing said switch arm to a corresponding one of said operating pc'Jsitions, means associated with some of said operating positions for effecting the tuning-of said receiver in response to control signals" comprising only short'pulses, and means associated with other of said" positions for effecting changes in volume level in response to control'sig'nals including said longer pulse, the extent of said volum'eflevel change being a function of the duration of said longer pulses p d .v 25. In a control systern'i for; a radio receiver having a gain control device, the provision of controllable driving means coupled to said gain control device for effectingchange in the output volume level of said receiver, means for generating? a" control signal including an impulse of controllable duration, means including a stepping; mechanism at said receiver for actuating said-controllablemeans in response to said control signal, said stepping mechanism being responsive to the duration of said controllable imchange in volume level," and means for homing said-stepping mechanismupon the termination of'said controllable impulse.

26.Ina control system for a radio receiver vice'to its home position, means for generating a control signal including arrinipulse of 'control-, lable-duration, stepping' me'ans responsiv to the total number-of impulses'in' said control signal for op'eratingsaid step-by-step' device to" effecta volumeincrease or decrease and for'controlling theextent of the volume variation acccr'd'ing to the-duration" of saidcontr ollable impulse, and mean's'for returning saidste'p y s'tep 'device to home. position after a predetermined "time in} terval following the' initiation of said impulses, said-'istepping means" r vent ng" return of the stepeby-step device to homeposition' if. said in terval terminates }withii'i'the"duration of said "controllable impulse? pulse for controlling the magnitude; of the' positions, J means urging saidstep by ste'p' d e- 2'7. The combination with a radio receiver pro: vided with an operable volume control device and electric driving means for operating the vol ume control device, of a step switch mechanism connected with said electric driving means for selectively controlling the operation thereof, operation of said step switch mechanism to a predetermined one of its positions acting to operate the volume control device substantially continuously and relatively slowly toward one extreme control position thereof and in another predetermined position to operate the volume control device in the same manner but toward the other extreme control position thereof, means for selectively generating and transmitting pulses of controlling signal currents, the number of pulses transmitted during any one cycle of operation of said last named means being determined by the number of steps it is desired to advance the step switch mechanism from its home position, means including a relay device having a predetermined time delay for returning the step switch to its home positionafter a. time interval which is appreciably-longer than the time interval between successive pulses of a train of control pulses during any cycle of operation whereby said step switch assumes its home position after the last pulse of a cycle of operation, and operable means for extending the time of transmission of the last impulse of the cycle of operation to thereby maintain the step switch in the desired position a length of time determined by the degree of volume change desired.

28. In a control system for a radio receiver, means for producing a train of electrical control impulse signals of predetermined periodicity, a stepping mechanism comprising a movable contact and a banlg of stationary contacts, said bank including at least one dead first contact and a plurality of, active contacts, means opere by the. engagement of said movable contact with said active contacts for effecting a control iunction at the receiver, a stepping coil associated With said stepping mechanism for advancing said movable contact from a zero position to said dead and active contacts, means for supplying said control signals to said stepping coil, and means for preventing disturbance impulses of periodicity difierent than that of said control signals from advancing said movable contact beyond said dead contact.

29. In a remote control system, apparatus to be controlled located at a first point, apparatus at a second and remote point for controlling said first-mentioned apparatus, means at said second point for generating an electrical wave, means for keying said wave generator to produce a number of short pulses of predetermined duration, auxiliary means associated with said keying means for keying said generator to produce.

at least one short pulse followed by a longer pulse of controllable duration, a step-by-step switching means at said first point having a movable switch arm and a plurality of selectable operating positions, positioning means responsive to the number of said short and long pulses for advancing said switch arm to a corresponding one of said operating positions, means associated with some of said operating positions for effecting a control function, and means associated with other of said operating positions for efiecting a difierent control function, the magnitude of said last-named control being a function of v the duration of said longer pulse, I

30. In a remote control system for radio receivers, means for producing a train of electrical control impulse signals, a stepping mechanism comprising a movable contact and a bank of stationary contacts, said bank including at least one dead first contact and a plurality of active contacts, a stepping coil associated with said stepping mechanism for advancing said movable contact from a zero position to said dead and active contacts, means for supplying said control signals to said stepping coil, apparatus; connected with said active contacts for control-- ling the operation of said receiver in response to said control signals, and means responsive to random disturbance impulses for returning saidl movable contact to zero position after a predetermined time interval following the initial dis-- turbance impulse, said last-named means tending to prevent widely spaced disturbance impulses from advancing said movable contact beyond said dead contact.

31. In a control system for a radio receiver, a stepping mechanism comprising a movable contact and a bank of stationary contacts, means controlled by said mechanism for efiecing receiver control functions, stepping means for advancing said movable contact in response to control signals, homing means for effecting the release of said movable contact, a common primary energy supply means for said stepping means and said homing means, switching means operable to simultaneously deenergize said steppingmeans. and said supply means, and capacitive means in-- ter-posed between said supply means and said! homing means for maintaining said homing: means energized for a short interval to thereby, insure homing of said mechanism after each. usage of the control system.

32. In a remote control system for a radio re-- ceiver wherein for any one selecting cycle a pre-- determined number of controlling pulses of:

signal currents are transmitted from the remote:-

point to the control point, the number thereof being determined by the controlling action desired, a plurality of selectable circuits at the receiver each acting upon selection thereof to effect a predetermined controlling action, a step switch device at the receiver having a plurality of contact positions corresponding to said selectable circuits, each of said contact positions being con nected with its associated circuit, said step switch being arranged to select any one of said circuits,

a stepping coil mechanism for the step switch device arranged to advance the step switch step by step from an initial starting position to any one of said plurality of contact positions to thereby select one of the circuits, means at the receiver for receiving the controlling pulses transmitted from the remote point and excitingthe stepping coil mechanism in accordance therewith, whereby upon receipt of the controlling pulses representing a selecting cycle said. step switch device is advanced from its starting position to a position corresponding to the num-- ber of pulses of signal currents received, and means including a relay device having a prede-- termined time delay for automatically returning: said step switch device to its-initial starting; position.

33. In a remote control system for a radio re--' ceiver wherein for any one selecting cycle a pre-- determined number of controlling pulses of signal currents are transmitted from the remote point to the control point, theinumber thereof being determined by the controlling action dc sired, means at the remote point for generating said pulses, a plurality of selectable circuits at the receiver each acting upon selection thereof to effect a predetermined controlling action, a step switch device at the receiver having a plurality of contact positions corresponding to said selectable circuits, each of said contact positions being connected with its associated circuit, said step switch being arranged to select any one of said circuits, a stepping coil mechanism for the step switch device arranged to advance the step switch step by step from an initial starting position to any one of said plurality of contact positions to thereby select one of the circuits, means at the receiver for receiving the controlling pulses transmitted from the remote point and exciting the stepping coil mechanism in accordance therewith, whereby upon receipt of the controlling pulses representing a selecting cycle said step switch device is advanced from its starting position to a position corresponding to the number of pulses of signal currents received, means including a relay device having a predetermined time delay for automatically returning said step switch device to its initial starting position, and operable means at the remote point for extending the time of transmission of a controlling pulse to thereby maintain the step switch device in a desired position a length of time determined by the degree of controlling action desired.

34. In a remote control system, a controlled radio receiving station and a controlling station remote from said receiving station, said controlling station including means operative selectively to transmit various trains of consecutive electrical impulses consisting of different numbers of impulses respectively, a first one of said trains, consisting of a small number of impulses, being effective to cause a volume increase at said receiving station, a second of said trains, consisting of a small but different number of impulses, being effective to cause a volume decrease at said receiving station, others of said trains, consisting in each case of larger numbers of impulses, being effective each to tune the receiver at said receiving station to a particular signal carrier frequenc individually, said receiving station comprising, in addition to the aforementioned receiver, common means operative in response to said first and second trains of impulses to increase and decrease, respectively, the output volume of the receiver, and further operative in response to said other trains to tune said receiver in conformity with the number of impulses constituting the particular received tuning train.

35. In a remote control system, a controlled radio receiving station and a remotely situated control station, there being only a space medium interconnecting said stations, means at said control station for generating and transmitting via said space medium a variety of trains of electromagnetic impulses, which trains are mutually differentiated by the number of impulses of which they are respectively constituted, manually controlled means at said control station for selectively determining which of said trains is to be transmitted, said controlled station comprising a radio receiver and control means selectively responsive to said trains of impulses to tune said receiver and to regulate the output volume thereof, said control means including a step-by-step selector switch having a multiplicity of fixed contacts and a movable contact operative to engage said fixed contacts consecutively and individually, said controlled station also comprising a plurality of local circuits, each including, individually, one of said fixed contacts and arranged to be closed only when said movable contact engages its individually associated fixed contact, each of said local circuits being effective, when completed, to tune said receiver to a particular radi channel, individually, said controlled station also comprising two additional local circuits, each including, individually, one of said fixed contacts and arranged to be closed. only when said movable contact engages its individually associated fixed contact, one of said additional local circuits being effective, when completed, to cause an increase in the output volume of said receiver, the other of said additional local circuits being effective, when completed, to cause a decrease in the output volume of said receiver, said control means also including an actuating electromagnet responsive to incoming electromagnetic impulses to move said movable contact proportionately, in each instance, to the number of received impulses constituting the incoming train, and means at said controlled station, independent of said remote control station, for automatically returning said movable contact to a predetermined starting point following each completed operation thereof, thereby conditioning said selector switch for a succeeding operation.

36. In combination, a remote control station including means operative to propagate into space, individually and selectively a plurality of signal trains, each consisting of a predetermined number of closely spaced consecutive impulses, each of which impulses is composed, in turn, of a continuous series of high frequency electromagnetic oscillations, each of said trains being differentiated from all the others by the number of said impulses of which it is composed; and a controlled station remote from said control station and connected therewith only through the space medium, said controlled station comprising a radio receiver and control equipment therefor which is selectively responsive to said trains of impulses to tune said receiver selectively to various predetermined radio channels and to regulate the output volume of said receiver, said controlled station including a plurality of individual local circuits and selector means for selectively actuating said circuits in response to trains of impulses received from said remote control station, the selection being determined by the number of impulses constituting the received train, certain of said local circuits being effective, when selected and actuated, to cause a variation of receiver output volume, others of said local circuits each being effective, when selected and actuated, to tune said radio receiver to a particular radio channel, means at said controlled station operative automatically to deactuate said selector means following each volume change operation thereof, whereby to retain the regulation of volume under control of the operator at said remote control station, and means at said controlled station for automatically restoring said selector means to a predetermined normal condition after a tuning operation has been performed and preparatory to a succeeding tuning operation.

MILTON L. THOMPSON. 

